Pump with a direct thrust recovery device for driving fluids

ABSTRACT

The invention relates to a pump with a direct thrust recovery device for driving fluids, formed by pumping mechanisms formed by pistons ( 4 ) which are actuated in reciprocating longitudinal movement, the corresponding piston ( 4 ) playing in each pumping mechanism between two chambers ( 6  and  7 ), through one of which the passage of the fluid to be pumped is established, whereas in the other chamber the reject flow of the applied system enters and exits, such that said reject flow acts to directly thrust the piston ( 4 ), exerting a complementary action of the drive thereof.

FIELD OF THE ART

The object of the invention relates to pumping liquids in systems having a reject stream with energy that can be recovered, such as reverse osmosis desalination, proposing a positive displacement pump including in a single unit the functional pumping assembly and the reject energy recovery assembly for recovering the energy which is to be harnessed, using said reject energy as a direct thrust complement for driving the pumping.

STATE OF THE ART

There are fluid displacement systems in the industrial field which involve a reject stream with energy that can be harnessed, such as reverse osmosis desalination processes, in which a salt water stream is supplied at a certain pressure, fresh water and reject brine being obtained with a pressure close to that of the feed stream.

In reverse osmosis desalination water is pumped at 60 bars to the desalination membranes, approximately 45% fresh water and 55% brine (reject) being obtained, such that the fresh water exits without pressure (0 bars), whereas the reject exits at a pressure between 1 and 1.5 bars lower than that of the feed, i.e., between 58.5 and 59 bars, this reject pressure having an energy which can be harnessed.

The solutions currently used to harness reject flow energy in desalinators use independent mechanisms to actuate complementary feed pumping:

A) By means of Pelton turbines consisting of centrifugal pumps, coupled to the shaft of which there is a desalinator reject energy flow recovery mechanism, such that by means of said mechanism a complementary torque is applied to the motor of the corresponding pump, thereby reducing the energy needed to actuate the motor.

B) By means of isobaric chambers which use the actual reject fluid to exert the thrust necessary to perform pumping through a feed pump the efficiency of which is 96-97%.

In this case, since isobaric chambers must work at 60 bars and the reject of the desalinators exits at 58.5-59 bars, if this reject is introduced directly into the feed pump, the efficiency of which is 96-97%, only 58 bars are obtained at its outlet, such that it is necessary to place a complementary pump providing an increase of 2 bars so that the feed enters the isobaric chamber at the necessary 60 bars.

This arrangement forces controlling the streams supplied by the primary pump and by the complementary pump, which are mixed in the feed, having to perfectly synchronise them, requiring very complex, complicated and expensive controls.

In addition, it has been technically accepted that positive displacement systems have a higher efficiency than centrifugal systems, but in the current market there are no positive displacement pumps providing large streams, whereby existing pumps of this type are not applicable in desalination systems.

OBJECT OF THE INVENTION

According to the invention a positive displacement pump is proposed, the embodiment of which has been provided with features which allow supplying a large stream, therefore allowing the application in systems such as desalination systems and the like given the high efficiency which is achieved.

This pump object of the invention consists of a functional assembly integrating in one and the same structural unit the pumping system and a reject fluid energy recovery system by means of a piston which is actuated by a crankshaft which can play between two chambers provided with respective pairs of conflicting valves controlling the closure and the opening of respective inlets and outlets of said chambers, those valves being controlled synchronously by the same drive of the crankshaft actuating the piston.

A functional assembly is thus obtained which allows establishing the passage of the fluid to be pumped through one of the chambers between which the piston plays, whereas the passage of the reject flow the energy of which is to be harnessed can be established through the other chamber, such that said reject flow energy is used to drive the forward movement of the piston in the pumping action, complementing the action of the crankshaft.

The reject flow energy is thus directly harnessed in the actual impulse pump of the fluid to be pumped, said reject flow energy being used as a complementary actuation of the drive of the piston of the pump, a very high pumping efficiency being achieved.

With very little external drive energy, pumping can thus be obtained with the pressure necessary for reverse osmosis desalination systems or other similar systems, harnessing the energy of the actual reject flow of the system as energy for driving the impulse pump of the pumping, thus optimising energy consumption without the need for complicated controls like those which isobaric chamber systems require.

Furthermore, given that the recovery device acts by thrust, no regulation and control system is necessary to ensure the continuous balance and continuity between the stream which is pumped with the pump and that which is pumped by the recovery device. In addition, since the displacement recovery device is positive, the conversion of the reverse osmosis process is maintained permanently, it only being necessary to act on the pumping stream if a constant water quality is to be maintained, and the progressive increase of load loss in reverse osmosis membranes over time between the processes for cleaning said membranes can be compensated by providing higher torque in the mechanical drive.

The pump with a direct thrust recovery device is also perfectly suitable for changing the operating conditions or revolutions, being especially suitable for working driven by variable speed drives, such that the reject discharge volume can therefore be regulated at source, for its adaptation to different types of installations according to needs, such as for example:

Installation of desalinators on the coast, with discharge of the reject out to sea, wherein the necessary pipes involve a high cost, such that to reduce the diameter of the pipes carrying the discharge to the open sea, it is necessary to return the lower reject volume.

Installation of desalinators on the open sea, in which the rejects are discharged directly into the sea without the need for carrying pipes, the discharge volume being able to be large.

Installation of underground desalinators, for example under a seafront, in which a large reject volume can be of interest, so that it lowers the concentration and can be discharged near the coast.

The valves of the chambers between which the piston of the pump plays are of a rotary type, being actuated by a common transmission determining a desmodromic distribution, forming a synchronised intake and drive system in each of the chambers, with synchronised relation at the same time between the systems of both chambers.

In the arrangement of the assembly the piston of the pump is arranged with a ceramic-type gasket-free sealing system which does not require maintenance, being able to be complemented with a pressure sealing system compensated with lubrication, a wear-free arrangement with minimal volumetric loss being achieved.

Therefore, said valve object of the invention has certainly advantageous features, acquiring its own identity and preferable character with respect to the conventional solutions for the function for which it is intended.

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view of a practical embodiment of the pump object of the invention.

FIG. 2 is a perspective view from another angle of the pump of the previous figure.

FIG. 3 is a frontal view of the pump sectioned by the pumping body.

FIG. 4 is sectioned side view of the pump assembly.

FIG. 5 is a longitudinal section of a fundamental pumping mechanism of the pump.

FIGS. 6 and 7 depict two positions of the pumping mechanism in the suction phase.

FIGS. 8 and 9 depict two positions of the pumping mechanism in the drive phase.

FIG. 10 is a detail of the gasket-free sealing assembly of the piston of the pumping mechanism.

FIG. 11 is a detail of the sealing assembly with a compensated pressure chamber and lubrication of the piston of the pumping mechanism.

DETAILED DESCRIPTION OF THE INVENTION

The object of the invention relates to a pump intended for driving fluids in systems producing a reject stream with an energy which can be harnessed, such as reverse osmosis desalinators or similar systems, with an embodiment including the pumping system and the reject energy recovery system in one and the same functional assembly.

As seen in FIGS. 1 and 2, in its general assembly the pump of the invention comprises a body (1) in which the pumping system and the reject energy recovery system are included, a body (2) in which the drive system and a motor (3) actuating the drive are included.

The pumping system can comprise multiple combined action mechanisms integrated in respective pistons (4) which are actuated in longitudinal movement by a crankshaft (5) driven by the motor (3), as is inferred from FIGS. 3 and 4.

According to FIG. 5, each mechanism of the pumping system acts in relation to two chambers (6 and 7), between which the corresponding piston (4) plays in its displacement actuated by the crankshaft (5), such that the front part of the piston (4) moves in one (6) of said chambers, whereas the rear part of the same piston (4) moves in the other chamber (7).

The chamber (6) has an inlet (8) and an outlet (9), in which respective opening and closure valves (8.1 and 9.1) act, whereas the chamber (7) in turn has a respective inlet (10) and a respective outlet (11), in which respective opening and closure valves (10.1 and 11.1) also act.

The valves (8.1, 9.1, 10.1 and 11.1) are rotary type valves and are all actuated in common, by means of a transmission belt (12) from the shaft of the crankshaft (5), such that the drive of said valves is synchronised with regard to one another and at the same time synchronised with the movement of the piston (4) of the pumping mechanism.

In these conditions, by establishing, for example, the passage of a fluid to be pumped, such as the feed salt water into a reverse osmosis desalinator through the chamber (6), and the passage of the reject flow of the system (brine in the case of the mentioned example) through the chamber (7) when the pumping mechanism is actuated, when the piston (4) moves back, as depicted in FIG. 6, the inlet (8) of the chamber (6) is open and the outlet (9) closed, whereas the inlet (10) of the chamber (7) is closed and the outlet (11) open, whereby the fluid to be pumped is suctioned towards the chamber (6) through the inlet (8), whereas the reject fluid which is in the chamber (7) is expelled through the outlet (11) thereof.

That situation is maintained until the piston (4) reaches the backwards limit of movement, at which time the valves (8.1 and 11.1), which have been rotating, reach the closure position for closing the respective inlet (8) and outlet (11), whereas the valves (9.1 and 10.1), which have also been rotating, reach the position of commencing the opening of the outlet (9) of the chamber (6) and of the inlet (10) of the chamber (7), respectively, as seen in FIG. 7.

When the piston (4) reaches the backwards limit of movement, the movement thereof is reversed to forward displacement, during which the inlet (8) of the chamber (6) remains closed and the outlet (9) open, whereas the inlet (10) of the chamber (7) is kept open and the outlet (11) closed, as is seen in FIG. 8.

In this phase, the displacement of the piston (4) causes the fluid which is in the chamber (6) to be driven through the outlet (9), whereas the reject flow reaches this phase with the pressure which it has in the chamber (7), such that the displacement of the piston (4) in this situation is caused by the action of the crankshaft (5) and by the thrust that the reject flow exerts in the chamber (7) on the rear part of the actual piston (4), such that the drive energy which the motor (3) must supply to the crankshaft (5) is reduced to the extent of the direct thrust action with which the reject flow on the piston (4) collaborates.

The situation of driving the fluid to be pumped from the chamber (6), with thrust collaboration from the reject flow, is maintained until the piston (4) reaches the forward displacement limit, at which time the valves (9.1 and 10.1), which have been rotating, reach the closure position for closing the respective outlet (9) and inlet (10), whereas the valves (8.1 and 11.1), which have also been rotating, reach the position of commencing the opening of the inlet (8) of the chamber (6) and of the outlet (11) of the chamber (7), respectively, as is seen in FIG. 9.

Thus, by means of the reciprocating longitudinal displacement of the piston (4), a series of cycles with alternating phases is obtained, i.e., a suction phase through the inlet (8) and a drive phase through the outlet (9), in the chamber (6), a continuous pumping of the fluid to be pumped being obtained, while at the same time in the chamber (7) a corresponding alternation of phases occurs, i.e., reject flow arrival and evacuation phases, the energy of said reject flow being harnessed to thrust the piston (4) as a necessary complement of the drive, the energy that the drive motor (3) must provide thus being reduced, with the entire functional assembly of both the pumping system and of the reject flow energy harnessing system in one and the same structural unit.

The passage of the fluid to be pumped through the front chamber (6) and the reject flow energy harnessing in the rear chamber (7) is a preferred form, because of the efficiency that is obtained, but without the concept of the pump according to the invention being altered, the arrangement could equally be the reverse, since the operation is similar.

In the arrangement of the assembly, the piston (4) is incorporated with a sealing system (13) between the chambers (6 and 7) of the functional pumping assembly and with another sealing system (14) in the rear part between the chamber (7) and the body (2) of the drive mechanism, means of the sealing system (13), not very demanding with regard to seal, being required between the chambers (6 and 7), since the pressure difference between the pumping chamber (6) and the reject energy recovery chamber (7), is very small (1-1.5 bars).

In addition, the configuration of the piston (4) is determined with the rear part projecting towards the body (2) of the drive mechanism, with a considerably small diameter in comparison with the actual piston (4) itself, which favours the action of the complementary thrust by the reject flow, whereas the means of the sealing system (14) are arranged in a small circumferential dimension, so the loss area that they must close is very small.

For the purpose of minimising wear problems caused by the seawater to the materials, the outer peripheral areas of the piston (4) which have to contact the sealing systems (13 and 14) are structured with materials which are very hard and resistant to corrosion, such as aluminium oxide, silicon carbide, tungsten carbide, etc.

And for that same purpose, the sealing systems (13 and 14) are structured with ceramic rings (15), as in the example of FIG. 10, a controlled partial sealing being determined with regard to its dimensions and therefore the percentage of leaks, which aid in the sliding and act as a coolant.

The sealing systems (13 and 14) can also be structured as in the embodiment of FIG. 11, with a controlled partial sealing ceramic ring (15) and an additional closure complement made up of a double sealing gasket assembly (16), with an intermediate chamber (17) which is pressurised by means of an external supply of lubricating fluid.

In this case the chamber (17) is pressurised to a pressure equal to or somewhat higher than the pressure of the reject flow energy recovery chamber (7), whereby the level of leaks through the sealing closure is minimal or nil.

It is therefore a sealing system suitable for the conditions of a very corrosive and abrasive fluid, such as sea water, closure with respect to the exterior being the responsibility of the gaskets (16) but with the lubrication of the fluid of the chamber (17), such that the useful life of said gaskets (16) is similar to that which is achieved in oil hydraulic systems.

Although in the description the use of the proposed pump in reverse osmosis desalination systems has been assumed, it is only a non-limiting example of an application since said pump object of the invention can be applied in the same conditions in any system requiring a moving fluid and causing a residual flow provided with certain energy, such as for example the hydraulic drive of a turbine from where the drive flow is removed to the drainage channel with an energy which could be harnessed to aid pumping the same water at the level from where the driving flow of the turbine falls. 

1. A pump with a direct thrust recovery device for driving fluids, of the type comprising one or more pumping mechanisms formed by respective pistons which are actuated in reciprocating longitudinal movement to drive a feed fluid into a system in which a reject flow provided with an energy which can be harnessed is produced, characterized in that each pumping mechanism includes in one and the same structural and functional unit the pumping system and the reject flow energy recovery system by means of a piston (4) playing between two chambers (6 and 7), through one of which chambers the passage of the fluid to be pumped is established, whereas in the other chamber the reject flow the energy of which can be harnessed enters and exits, exerting a direct thrust on the piston (4), acting as a complement of the drive thereof in the pumping action.
 2. The pump with a direct thrust recovery device for driving fluids according to claim 1, characterised in that the chambers (6 and 7) between which the piston (4) plays have respective inlets (8 and 10) and respective outlets (9 and 11) in which corresponding opening and closing rotary valves (8.1, 9.1, 10.1 and 11.1) act, said valves being actuated synchronously by a common transmission, to determine alternating intake and expulsion phases in the pumping chamber and alternating reject flow energy inlet and outlet phases in the energy harnessing chamber, in combination with the displacements of the piston (4).
 3. The pump with a direct thrust recovery device for driving fluids according to claim 1, characterised in that the piston (4) is arranged with a sealing system (13) between the chambers (6 and 7) and with a sealing system (14) for sealing the outlet towards the exterior in the rear part, the sealing system (14) being incorporated on a rear extension with a smaller diameter than the body of the piston playing between the chambers (6 and 7).
 4. The pump with a direct thrust recovery device for driving fluids according to claim 3, characterised in that the sealing systems (13 and 14) of the piston (4) are determined with ceramic rings (15), a controlled partial sealing being established with leaks aiding in the sliding and acting as a coolant.
 5. The pump with a direct thrust recovery device for driving fluids according to claim 3, characterised in that the sealing systems (13 and 14) of the piston (4) are determined with a controlled partial sealing ceramic ring (15) and an additional closure complement made up of a double assembly of sealing gaskets (16) with an intermediate chamber (17) which is pressurised by means of the external supply of a lubricating fluid. 